feat(ui): add CorrespondenzHero with discovery headline and large typeahead

New centred hero component for the Briefwechsel page: headline
"Wessen Briefe möchten Sie lesen?", cross-link to document search,
h-14 PersonTypeahead, and recent persons chips. Adds `large` prop
to PersonTypeahead and `conv_hero_crosslink` message key.

Refs: #179

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/briefwechsel/CorrespondenzHero.svelte.spec.ts

@@ -0,0 +1,50 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+import CorrespondenzHero from './CorrespondenzHero.svelte';
+
+vi.mock('$app/navigation', () => ({ goto: vi.fn() }));
+
+afterEach(cleanup);
+
+const noop = () => {};
+
+describe('CorrespondenzHero — headline and cross-link', () => {
+	it('renders the discovery headline', async () => {
+		render(CorrespondenzHero, { onSelectPerson: noop });
+		await expect.element(page.getByText(/Wessen Briefe möchten Sie lesen/i)).toBeInTheDocument();
+	});
+
+	it('renders a cross-link to the document search page', async () => {
+		render(CorrespondenzHero, { onSelectPerson: noop });
+		const link = page.getByRole('link', { name: /Zur Dokumentensuche/i });
+		await expect.element(link).toBeInTheDocument();
+		await expect.element(link).toHaveAttribute('href', '/');
+	});
+
+	it('renders a person typeahead input', async () => {
+		render(CorrespondenzHero, { onSelectPerson: noop });
+		await expect.element(page.getByTestId('conv-hero').getByRole('textbox')).toBeInTheDocument();
+	});
+});
+
+describe('CorrespondenzHero — recent persons', () => {
+	it('shows recent person chips when provided', async () => {
+		render(CorrespondenzHero, {
+			onSelectPerson: noop,
+			recentPersons: [{ id: 'r1', name: 'Clara Braun' }]
+		});
+		await expect.element(page.getByText('Clara Braun')).toBeInTheDocument();
+	});
+
+	it('calls onSelectPerson when a recent person chip is clicked', async () => {
+		const spy = vi.fn();
+		render(CorrespondenzHero, {
+			onSelectPerson: spy,
+			recentPersons: [{ id: 'r1', name: 'Clara Braun' }]
+		});
+		await expect.element(page.getByText('Clara Braun')).toBeInTheDocument();
+		document.querySelector<HTMLElement>('[data-testid="recent-person-r1"]')!.click();
+		expect(spy).toHaveBeenCalledWith('r1');
+	});
+});